JP2015036672A - Radar signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar signal processor capable of detecting primary echo without being affected by secondary echo.SOLUTION: A modulator (A)2 modulates a pulse by using a code sequence 1. A modulator (B)3 modulates a pulse by using a code sequence 2. A reflection signal of a transmitted pulse modulated with the code sequence 1 and a reflection signal of a transmitted pulse modulated with the code sequence 2 are received by a receiver 7, demodulated by a demodulator (A)8 by using the code sequence 1, and further demodulated by a demodulator (B)9 by using the code sequence 2. The signals are subtracted by a subtracter 11, and only primary echo is extracted.

Description

  The present invention relates to a radar signal processing device, and more particularly to a radar signal processing device for removing multi-order echoes in a pulse radar device.

  For example, weather radar detects the intensity of echoes reflected by rain particles such as clouds and rain, and uses the Doppler effect of reflected waves to detect dynamic changes in rain and clouds in order to observe or predict weather conditions. A pulse Doppler radar that can be captured is used.

In general, in a pulse radar apparatus, a transmission pulse is repeatedly emitted at a required repetition interval. This pulse repetition period is determined corresponding to the maximum distance of the target (primary echo) to be detected.
Therefore, since the reflected wave (secondary echo) from the target farther than the maximum distance returns after the next transmission pulse is emitted, it is recognized as if it is present at a short distance. Further, such a secondary echo is superimposed on the primary echo and may deteriorate the detection accuracy of the primary echo, and thus needs to be removed.

  In order to solve such problems, for example, methods as disclosed in Patent Documents 1 to 3 and Non-Patent Document 1 have been proposed. In Patent Document 1, a method of performing phase modulation using a code string whose polarity is reversed for each hit, and in Patent Document 2, a method of modulating a transmission pulse signal with a modulation method having a low correlation with at least one previous transmission pulse signal, In Patent Document 3, a phase modulation method using a sequence called an SZ code sequence is used. In Non-Patent Document 1, a phase modulation method using a sequence called a pseudo-random code sequence is used.

  Then, the primary echo based on the transmitted transmission pulse signal and the secondary echo based on the transmission pulse signal at least one prior to the transmission pulse signal are received and demodulated by a corresponding demodulation method to perform signal processing.

  When correlation is made for a plurality of hits, the demodulated primary echo components are piled up and the secondary echo components cannot be correlated and are dispersed. In the Doppler spectrum as a dispersed form, in Patent Document 3, it is spread only to a specific frequency, and in Non-Patent Document 1, it is converted to white noise. The conventional secondary echo removal method is configured as described above, and the detection accuracy of the primary echo is improved by reducing the signal of the secondary echo.

JP-A-6-138215 JP 2002-139565 A US Pat. No. 6,081,221

Shoichiro Fukao and Kyosuke Hamatsu, “Radar Remote Sensing of Weather and Atmosphere [Revised 2nd Edition]”, Kyoto University Academic Press, July 24, 2009, p.285-287

  However, for example, in a weather radar, when the intensity of a secondary echo is higher than that of a primary echo, such as a mountain or a typhoon that exists in the distance, the primary echo is scattered in the secondary echo component diffused on the Doppler spectrum. Therefore, the methods such as Patent Document 1, Patent Document 2, and Non-Patent Document 1 have a problem that the detection accuracy of the primary echo deteriorates.

  Further, in Patent Document 3, since the secondary echo component is diffused only to a specific frequency, the primary echo and the secondary echo can be separated in the frequency domain in principle, and the intensity of the secondary echo is higher than that of the primary echo. The detection accuracy of the primary echo does not deteriorate even when the frequency is high. However, when the velocity width (spectrum width) of the primary echo or the secondary echo is wide, there is a problem that the detection accuracy of the primary echo deteriorates.

  The present invention has been made to solve the above-described problems. The primary echo is not affected by the secondary echo even when the velocity range is wide, regardless of the intensity of the secondary echo. An object of the present invention is to obtain a radar signal processing apparatus capable of detecting the above.

  The radar signal processing apparatus according to the present invention includes a transmission means for transmitting a pulse using a first code sequence and a second code sequence as two types of phase modulation sequences, and a transmission pulse modulated with the first code sequence. A multi-order echo removing means for matching the phase difference applied to the multi-order echo with the phase difference applied to the multi-order echo of the transmission pulse modulated by the second code sequence, and subtracting them to extract only the primary echo; It is provided.

  The radar signal processing apparatus according to the present invention matches the phase difference applied to the multi-order echo of the transmission pulse modulated by the first code sequence with the phase difference applied to the multi-order echo of the transmission pulse modulated by the second code sequence. Since these are subtracted to extract only the primary echo, the primary echo can be detected without being affected by the multi-order echo.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the radar signal processing apparatus by Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the radar signal processing apparatus by Embodiment 1 of this invention. It is a block diagram which shows the radar signal processing apparatus by Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the radar signal processing apparatus by Embodiment 3 and 4 of this invention. It is explanatory drawing which shows the mode of the spectrum of the received wave which enters into the amplitude corrector of the radar signal processing apparatus by Embodiment 3 of this invention. It is a block diagram which shows the radar signal processing apparatus by Embodiment 4 of this invention.

The radar signal processing apparatus of the present invention uses a first code sequence and a second code sequence as two types of phase modulation sequences in a radar that suppresses secondary echo by phase modulation, and uses the first code sequence 2 Only the desired primary echo is extracted by combining and subtracting the phase difference applied to the secondary echo and the phase difference applied to the secondary echo of the second code sequence.
The present invention is also effective for multi-order echoes other than the secondary echo. Hereinafter, the case of the secondary echo will be described as an example.

The basic principle is shown below.
For example, when the transmission pulse is phase-modulated with a predetermined code sequence 1 (first code sequence), the phase applied to the reflected signal from the primary echo is Φ ₁ and the phase applied to the reflected signal from the secondary echo is Φ _2. When the phase modulation is performed with a predetermined code sequence 2 (second code sequence), the phase applied to the reflected signal from the primary echo is φ ₁ and the phase applied to the reflected signal from the secondary echo is φ ₂ .

When the phase -Φ ₁ is applied to the reception pulse modulated by the code sequence 1, the phase applied to the reflected signal from the primary echo becomes 0, but the phase applied to the reflected signal from the secondary echo is Φ ₂ -Φ. Remains as ₁ . Similarly, when applying a phase -.phi ₁ for the received pulse modulated with the code sequence 2, the phase becomes 0 according to the reflected signals from the primary echo, the phase according to the reflected signals from the secondary echo φ It remains a _{2 -φ 1.} Here, the code sequences 1 and 2 are selected so that Φ ₂ −Φ ₁ = k (φ ₂ −φ ₁ ) (k is a constant other than 0 and ₁ ).

Next, the phase (k−1) (φ ₂ −φ ₁ ) is changed with respect to the received pulse modulated by the code sequence 2 so that the phases applied to the reflected signals from the secondary echo are both φ ₂ −Φ _1. Further, the phase applied to the reflected signal from the primary echo is (k−1) (φ ₂ −φ ₁ ), and the phase applied to the reflected signal from the secondary echo is k (φ ₂ −φ ₁ ), that is, Φ ₂ −Φ ₁

When these two received signals are subtracted, the reflected signal from the primary echo remains out of phase because the phases are different, but the reflected signal from the secondary echo is canceled because the phases are matched. Therefore, only the primary echo can be extracted.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a radar signal processing apparatus according to Embodiment 1 of the present invention.
This apparatus includes an oscillator 1, a modulator (A) 2, a modulator (B) 3, a transmitter 4, a circulator 5, an antenna (antenna) 6, a receiver 7, a demodulator (A) 8, and a demodulator (B). 9, a modulator (C) 10, a subtractor 11, a corrector 12, and an intensity / speed / speed width calculator 13.

  The oscillator 1 is an oscillator that generates a pulse that serves as a seed signal for use by the modulator (A) 2 and the modulator (B) 3. Modulator (A) 2 is a modulator based on code sequence 1, and modulator (B) 3 is a modulator based on code sequence 2. The transmitter 4 is a transmitter for transmitting the pulses modulated by the modulator (A) 2 and the modulator (B) 3 from the antenna 6. Further, the modulator (A) 2, the modulator (B) 3 and the transmitter 4 transmit for transmitting a pulse using the first code sequence and the second code sequence as two types of phase modulation sequences. Means are configured. The circulator 5 is a circulator that supplies a transmission signal from the transmitter 4 to the antenna 6 and performs signal separation for transmitting the reception signal from the antenna 6 to the receiver 7.

  The receiver 7 is a receiver that receives the reflected signal of the transmission signal reflected from the detection target or the like via the antenna 6 and the circulator 5. The demodulator (A) 8 is a demodulator using the code sequence 1, and the demodulator (B) 9 is a demodulator using the code sequence 2. The modulator (C) 10 further performs phase modulation on the pulse output from the demodulator (B) 9 using the code sequence 2 in order to match the phases of the reflected signals from the two types of secondary echoes. It is a modulator for performing. The subtractor 11 subtracts the received pulse modulated by the code sequence 1 output from the demodulator (A) 8 and the received pulse modulated by the code sequence 2 output from the modulator (C) 10. It is a subtractor. The demodulator (A) 8 to the subtractor 11 constitute multi-order echo removal means. The corrector 12 is an arithmetic unit for returning the reflected signal from the primary echo remaining after the subtraction to the original form. The intensity / speed / speed width calculator 13 is a calculator that calculates the intensity, speed, and speed width of the primary echo based on the reflected signal from the primary echo output from the corrector 12.

Next, the operation of the first embodiment will be described. FIG. 2 shows a flowchart.
In order to generate two types of phase modulation sequences, the seed signal is generated by the oscillator 1 (step ST1), the phase modulation 1 is performed by the modulator (A) 2 based on the code sequence 1 (step ST2), and the code sequence 2 The modulator (B) 3 performs phase modulation 2 (step ST3), and the transmitter 4 outputs a transmission signal (step ST4).

At this time, the code sequence obtained by multiplying the phase of the code sequence 2 by a constant number other than 0 or 1 is selected to be the code sequence 1. For example, code sequence 1 and code sequence 2 are generated as follows.

  The transmission signal is radiated from the antenna 6 into the air and reflected by the observation target. As an example, the observation target in the weather radar system is rain particles present in a predetermined area. The reflected wave from the observation target is captured by the antenna 6 and received by the receiver 7 (step ST5). The receiver 7 sends received waves to the demodulator (A) 8 based on the code sequence 1 and the demodulator (B) 9 based on the code sequence 2.

となる。 The demodulator (A) 8 based on the code sequence 1 applies a phase so that the phase of the reflected signal from the primary echo is 0 with respect to the received pulse modulated by the code sequence 1 (phase demodulation 1, step ST6). . Further, the demodulator (B) 9 based on the code sequence 2 applies a phase so that the phase applied to the reflected signal from the primary echo is 0 with respect to the received pulse modulated by the code sequence 1 (phase demodulation 2, step ST7). For example, in order to demodulate a signal modulated by the code sequence represented by the above equation (1),
Code sequence 1: -Φ _m
Code sequence 2: -φ _m
, The phase applied to the reflected signal from the primary echo becomes zero.
At this time, the phase applied to the reflected signal from the secondary echo is

It becomes.

The modulator (C) 10 further applies phase modulation to the received pulse modulated by the code sequence 2 in order to match the phases of the reflected signals from the two types of secondary echoes (phase demodulation 3, step ST8). ).
For example, when the phases applied to the reflected signal from the secondary echo of the equation (2) are compared, there is a relationship of Φ _m−1 −Φ _m = 2 (φ _m−1 −φ _m ). Therefore, a phase (φ _m−1 −φ _m ) is further applied to the received pulse modulated by the code sequence 2.
As a result, the phase applied to the reflected signal from the primary echo is (φ _m−1 −φ _m ) with respect to the reception pulse modulated by the code sequence 2, and the phase applied to the reflected signal from the secondary echo is 2 ( φ _m−1 −φ _m ) = Φ _m−1 −Φ _m

A received wave having the same phase applied to the reflected signal from the secondary echo is sent to the subtractor 11 to subtract the two kinds of signals (step ST9).
For example, when the reception pulse modulated with the code sequence 2 is subtracted from the reception pulse modulated with the code sequence 1, the reflected signal from the secondary echo is canceled because it is modulated so that the code sequence 1 and the code sequence 2 are equal. On the other hand, the reflected signal from the primary echo remains without being canceled because the phase is different.

The reflected signal from the primary echo remaining after the subtraction is returned to the original form by the corrector 12 (step ST10).
For example, in this example, a subtraction of the primary echo with the phase (φ _m−1 −φ _m ) from the primary echo of phase 0 remains. Therefore, the original signal is restored by multiplying the remaining signal by 1 / (1-exp (−j (φ _m −φ _m−1 ))).

  Based on the reflected signal from the primary echo returned to its original form, the intensity / velocity / velocity width calculator 13 estimates the primary echo intensity p1, velocity v1, and velocity width w1 (autocorrelation processing, step ST11). ).

  As described above, according to the radar signal processing apparatus of the first embodiment, the transmission means for transmitting a pulse using the first code sequence and the second code sequence as the two types of phase modulation sequences, and the first The phase difference applied to the multi-order echo of the transmission pulse modulated with the code sequence is matched with the phase difference applied to the multi-order echo of the transmission pulse modulated with the second code sequence, and these are subtracted to obtain only the primary echo. Since the multi-order echo removing means for extracting is provided, it is possible to extract only the primary echo without the influence of the secondary echo. Further, in this method, it is possible to remove the secondary echo without specifying it, regardless of the shape of the secondary echo.

  Further, according to the radar signal processing apparatus of the first embodiment, the second code sequence and the first code sequence that is a phase modulation sequence obtained by multiplying the second code sequence by a constant are used as the specific phase modulation sequence. When the phase is matched with the transmission means for transmitting the pulse, the phase difference applied to the multi-order echo of the transmission pulse modulated with the first code sequence, and the primary echo of the transmission pulse modulated with the second code sequence Since there is provided a multi-order echo removing means for extracting only the primary echo by matching the phase difference applied to the multi-order echo and subtracting the phase difference of these multi-order echoes, the primary order is not affected by the secondary echo. It is possible to extract only the echo, and it is possible to remove the secondary echo without specifying it, regardless of the shape of the secondary echo.

  In addition, according to the radar signal processing apparatus of the first embodiment, the multi-order echo removing means is configured to perform subtraction of the phase difference in the time domain, so that only the primary echo is extracted without the influence of the secondary echo. Is possible.

Embodiment 2. FIG.
In the first embodiment, the code sequence 1 obtained by multiplying the phase of the code sequence 2 itself by a constant number other than 0 or 1 is used. However, the present invention can be similarly implemented when the phase difference is a constant multiple. This will be described below as Form 2. The configuration on the drawing is the same as that of FIG.

  The transmission unit in the second embodiment transmits a pulse using two types of phase modulation sequences that match the phase difference of the code sequence 1 when the phase difference of the code sequence 2 is multiplied by a constant, and the multi-order echo cancellation unit includes: The phase difference applied to the multi-order echo of the transmission pulse modulated by the code sequence 1 is matched with the phase difference applied to the multi-order echo when the phase is matched with the primary echo of the transmission pulse modulated by the code sequence 2. Only the primary echo is extracted by subtracting the phase difference of the multi-order echo.

実施の形態１の式（１）では、符号系列２を２倍したものが符号系列１となるように用いていたが、本実施の形態ではそのような関係にない。 Next, the operation of the radar signal processing apparatus in the second embodiment will be described.
For example, code sequence 1 and code sequence 2 are generated as follows.

In the formula (1) of the first embodiment, the code sequence 2 is doubled so that the code sequence 1 is used. However, in the present embodiment, there is no such relationship.

となり、式（２）と同様の形になる。つまり、１次エコーからの反射信号にかかる位相を０となるように位相をかけたときに２次エコーからの反射信号にかかる位相が０または１以外の定数倍であれば、２次エコーの位相を一致させることができるので、その後の処理は実施の形態１と同様となる。 However, the demodulator (A) 8 based on the code sequence 1 applies a phase so that the phase of the reflected signal from the primary echo is 0 with respect to the received pulse modulated by the code sequence 1, and is demodulated by the code sequence 2. When the phase applied to the reflected signal from the primary echo is set to 0 with respect to the received pulse modulated by the code sequence 1 in the device (B) 9, the phase applied to the reflected signal from the secondary echo is ,

Thus, the shape is the same as in equation (2). That is, when the phase applied to the reflected signal from the primary echo is set to 0, if the phase applied to the reflected signal from the secondary echo is a constant multiple other than 0 or 1, the secondary echo Since the phases can be matched, the subsequent processing is the same as in the first embodiment.

  As described above, according to the radar signal processing apparatus of the second embodiment, when the phase difference of the second code sequence that is the specific phase modulation sequence is multiplied by a constant, phase modulation different from that of the second code sequence is performed. Transmitting means for transmitting a pulse using two types of phase modulation sequences that match the phase difference of the first code sequence that is a sequence; and a phase difference applied to multi-order echoes of a transmission pulse modulated by the first code sequence; By matching the phase difference applied to the multi-order echo when the phase is matched with the primary echo of the transmission pulse modulated by the second code sequence, only the primary echo is obtained by subtracting the phase difference of these multi-order echoes. Therefore, it is possible to extract only the primary echo without the influence of the secondary echo.

Embodiment 3 FIG.
FIG. 3 is a block diagram showing a configuration of a radar signal processing apparatus according to Embodiment 3 of the present invention. This apparatus is configured to include an amplitude corrector 14 in addition to the configuration of the oscillator 1 to the strength / speed / speed width calculator 13 similar to that of the first embodiment shown in FIG. That is, the multi-order echo removing means in the third embodiment has an amplitude corrector 14 that corrects an amplitude shift between reception signals of a transmission pulse modulated by the code sequence 1 and a transmission pulse modulated by the code sequence 2. ing.

Next, the operation of the radar signal processing apparatus according to the third embodiment will be described. FIG. 4 is a flowchart showing the operation of the third embodiment. Note that this flowchart also serves as an explanation of the operation in the fourth embodiment to be described later.
In the flowchart of FIG. 4, the operations from step ST1 to step ST8 are the same as those in the first embodiment shown in FIG. In the third embodiment, the phase is demodulated by the demodulator (A) 8 in step ST6, and after the phase modulation is performed by the modulator (C) 10 in step ST8, the amplitude corrector 14 shifts the amplitude. Whether or not there is a deviation in amplitude is determined (step ST12), and amplitude correction processing is performed (step ST13). That is, when a difference occurs in the amplitude of two types of received signals, such as when transmitting pulses are alternately fired or when the angle of the antenna 6 is different, the phase is demodulated by the demodulator (B) 9 based on the code sequence 2 The amplitude difference is corrected by the amplitude corrector 14.

によって推定された値を用いる。ｘ_１（ｆ_１）はｘ_１（ｆ）の１番目の要素、^＊は共役、ａｂｓ（ ）は絶対値を示す。Ｒはｘ_１（ｆ）自体の振幅、Ｐはずれた分の振幅をとっている。 The state of the spectrum of the received wave entering the amplitude corrector 14 is shown in FIG. (A) is code sequence 1 and (b) is code sequence 2. In these figures, the vertical axis represents amplitude and the horizontal axis represents frequency. For example, the demodulated signal of the code sequence 1 is x ₁ (f), the reflected signal from the primary echo at that time is a (f), and the reflected signal from the secondary echo is b (f). X ₂ (f) is a signal after phase matching with the secondary echo of the code sequence 1 of the above, c (f) is a reflected signal from the primary echo at that time, and b '( f). At this time, assuming that the difference in amplitude between x ₁ (f) and x ₂ (f) is ω,
e (f) = x ₁ (f) −ωx ₂ (f)
Thus, the signal e (f) of only the primary echo can be extracted. At this time, ω is

The value estimated by is used. x ₁ (f ₁ ) is the first element of x ₁ (f), ^* is a conjugate, and abs () is an absolute value. R takes the amplitude of x ₁ (f) itself, and P takes the amplitude of the deviation.

  As described above, according to the radar signal processing apparatus of the third embodiment, the multi-order echo removing means receives the transmission pulse modulated with the first code sequence and the transmission pulse modulated with the second code sequence. Since the configuration includes an amplitude corrector that corrects an amplitude shift between signals, even when the amplitude of the secondary echo signal is different, two types of amplitude correction are performed by applying the amplitude correction to the received pulse modulated by the code sequence 2. The secondary echoes of the received signals match, and it is possible to extract only the primary echo without the influence of the secondary echo.

Embodiment 4 FIG.
FIG. 6 is a block diagram showing a configuration of a radar signal processing apparatus according to Embodiment 4 of the present invention. This apparatus includes a phase corrector 15 in addition to the oscillator 1 to the intensity / speed / speed width calculator 13 similar to that of the first embodiment shown in FIG. That is, the multi-order echo removing means in the fourth embodiment has a phase corrector 15 that corrects a phase shift between the received signals of the transmission pulse modulated by the code sequence 1 and the transmission pulse modulated by the code sequence 2. ing.

Next, the operation of the radar signal processing apparatus according to the fourth embodiment will be described with reference to the flowchart of FIG.
In the flowchart of FIG. 4, the difference from the third embodiment is that the phase corrector 15 determines whether or not there is a phase shift in step ST12, and the phase corrector 15 performs phase correction processing in step ST13. It is. That is, in the fourth embodiment, when there is a difference between the phases of two types of received signals (step ST12), such as when the transmission pulses are alternately emitted or the angle of the antenna 6 is different, the demodulator based on the code sequence 2 is used. (B) After demodulating the phase at 9, the phase corrector 15 corrects the phase difference (step ST13).

によって推定された値を用いる。ｘ_１（ｆ_１）はｘ_１（ｆ）の１番目の要素、^＊は共役、ａｎｇｌｅ（ ）は、括弧内の位相角［ｄｅｇ］の計算を示す。θは、ずれた位相の角度を示す。 For example, the demodulated signal of the code sequence 1 is x ₁ (f), the reflected signal from the primary echo at that time is a (f), and the reflected signal from the secondary echo is b (f). X ₂ (f) is a signal after phase matching with the secondary echo of the code sequence 1 of the above, c (f) is a reflected signal from the primary echo at that time, and b '( f). At this time, assuming that the phase difference between x ₁ (f) and x ₂ (f) is θ, if the signal shift is corrected by θ,
e (f) = x ₁ (f) −exp (jθ) x ₂ (f)
Thus, the signal e (f) of only the primary echo can be extracted. At this time, θ is

The value estimated by is used. x ₁ (f ₁ ) is the first element of x ₁ (f), ^* is conjugate, and angle () indicates calculation of the phase angle [deg] in parentheses. θ represents the angle of the shifted phase.

  As described above, according to the radar signal processing apparatus of the fourth embodiment, the multi-order echo removing means receives the transmission pulse modulated with the first code sequence and the transmission pulse modulated with the second code sequence. Since the phase corrector for correcting the phase shift between the signals is provided, even when the amplitude of the signal of the secondary echo is different, the amplitude correction is applied to the received pulse modulated by the code sequence 2 so that two kinds of signals can be obtained. The secondary echoes of the received signals match, and it is possible to extract only the primary echo without the influence of the secondary echo.

Embodiment 5 FIG.
Although the first to fourth embodiments are processes for subtracting the secondary echo in the time domain and extracting the primary echo, the process can be performed in the frequency domain, and this will be described as a fifth embodiment.

When the transmission pulse is phase-modulated with code sequence 1, the phase applied to the reflected signal from the primary echo is A ₁ , and the phase applied to the reflected signal from the secondary echo is A ₂ . At this time, A ₁ is a matrix obtained by performing FFT (Fast Fourier Transform) on the phase sequence applied to the reflected signal from the primary echo, and A ₂ is a phase sequence applied to the reflected signal from the secondary echo. An FFTed matrix is shown. Assuming that the FFT primary signal is E ₁ , the secondary signal is E ₂ , and noise N, the received signal V is
V = A ₁ E ₁ + A ₂ E ₂ + N
It can be expressed as. Further, when the transmission pulse is phase-modulated with the code sequence 2, the phase applied to the reflected signal from the primary echo is B ₁ , and the phase applied to the reflected signal from the secondary echo is B ₂ . At this time, B ₁ represents a matrix obtained by performing FFT on the phase sequence applied to the reflected signal from the primary echo, and B ₂ represents a matrix obtained by performing FFT on the phase sequence applied to the reflected signal from the secondary echo. At this time, the received signal Z is
Z = B ₁ E ₁ + B ₂ E ₂ + N
It can be expressed as.

となる。符号系列２の１次エコーは符号系列１と異なる位相を持つため減算しても消えることはなく、２次エコーは一致するため抑圧される。 When the phase of the primary echo is matched to each of the two types of code sequences, the result is as follows.

It becomes. Since the primary echo of the code sequence 2 has a phase different from that of the code sequence 1, it does not disappear even if it is subtracted, and the secondary echo matches and is suppressed.

  As described above, according to the radar signal processing apparatus of the fifth embodiment, the multi-order echo removing means is configured to perform subtraction of the phase difference in the frequency domain. It is possible to extract only the primary echo.

In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .
In the first to fifth embodiments, not only electromagnetic waves but also sound waves can be used.

  1 oscillator, 2 modulator (A), 3 modulator (B), 4 transmitter, 5 circulator, 6 antenna (antenna), 7 receiver, 8 demodulator (A), 9 demodulator (B), 10 modulation (C), 11 subtractor, 12 corrector, 13 intensity / speed / speed width calculator, 14 amplitude corrector, 15 phase corrector.

Claims (7)

Transmitting means for transmitting a pulse using a first code sequence and a second code sequence as two types of phase modulation sequences;
The phase difference applied to the multi-order echo of the transmission pulse modulated with the first code sequence is matched with the phase difference applied to the multi-order echo of the transmission pulse modulated with the second code sequence, and these are subtracted to 1 A radar signal processing apparatus comprising multi-order echo removal means for extracting only the secondary echo. Transmitting means for transmitting a pulse using a second code sequence as a specific phase modulation sequence and a first code sequence that is a phase modulation sequence obtained by multiplying the second code sequence by a constant;
The phase difference applied to the multi-order echo of the transmission pulse modulated with the first code sequence and the phase difference applied to the multi-order echo when the phase is matched with the primary echo of the transmission pulse modulated with the second code sequence And a multi-order echo removing means for extracting only the primary echo by subtracting the phase difference of these multi-order echoes. When the phase difference of the second code sequence that is a specific phase modulation sequence is multiplied by a constant, two types of phases that coincide with the phase difference of the first code sequence that is a phase modulation sequence different from the second code sequence Transmitting means for transmitting a pulse using a modulation sequence;
The phase difference applied to the multi-order echo of the transmission pulse modulated with the first code sequence and the phase difference applied to the multi-order echo when the phase is matched with the primary echo of the transmission pulse modulated with the second code sequence And a multi-order echo removing means for extracting only the primary echo by subtracting the phase difference of these multi-order echoes.   The multi-order echo removing means includes an amplitude corrector that corrects an amplitude shift between reception signals of a transmission pulse modulated with the first code sequence and a transmission pulse modulated with the second code sequence. The radar signal processing device according to any one of claims 1 to 3, wherein the radar signal processing device is characterized in that:   The multi-order echo removing means includes a phase corrector that corrects a phase shift between reception signals of a transmission pulse modulated with the first code sequence and a transmission pulse modulated with the second code sequence. The radar signal processing device according to any one of claims 1 to 4, wherein the radar signal processing device is characterized in that:   The radar signal processing apparatus according to claim 1, wherein the multi-order echo removing unit subtracts a phase difference in a time domain.   The radar signal processing apparatus according to claim 1, wherein the multi-order echo removing unit subtracts a phase difference in a frequency domain.

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